The near infrared technology plays an important role in defense industries, geological prospecting, optical fiber communication, environmental monitoring, biological imaging, food and drugs, and agricultural inspecting. The key to the development of the near infrared technology lies in the development of materials and the fabrication of light-emitting devices. Due to their small size, low power consumption, high stability, and long lifetime, near-infrared LEDs are critical media for implementing the infrared technology.
Near-infrared LEDs are commonly seen in general applications such as remote controllers and automatic doors of shops. In addition, they are also frequently adopted in transmission and storage of information as well as in the domain of optical fiber communication. Furthermore, in night-vision monitors, near-infrared light sources are applications of near-infrared LEDs. Although the near infrared cannot be sensed by human eyes, it can be captured by cameras or video recorders. Thereby, the near infrared is usually used for supplementing light at night or in places with insufficient brightness, so that monitoring cameras can catch images.
In addition to the night-vision or optical communication applications as described above, near-infrared LEDs can be applied to the biomedical domain. For example, the near infrared emitted by a near-infrared LED can be used to illuminate the skin of a user. Next, a spectrum detector is used for receiving the reflection light, and then the user's blood glucose level can be evaluated after calculations. Thereby, near-infrared LEDs can be applied to a non-invasive blood glucose meter; they can be applied to therapies of skin diseases.
Nonetheless, in the fabrication of near-infrared LEDs, very few of the light-emitting materials are soluble. Moreover, complicated chemical synthesis methods are mostly required, or complicated methods are required for synthesizing quantum dot materials with different diameters, which mostly contains lead and thus against the regulations of environmental protection. Besides, the manufacturing processes mostly require costly vacuum equipment, demanding substantially high fabrication investment.
The China Patent Application Number CN 200780017078.2 disclosed a light-emitting material capable of emitting light in the visible or near-infrared region. The dehydrated SnI2 and CsI are mixed in a standard mold filling machine with the ratio of 1 wt %˜99 wt % and ground for 1 to 24 hours. After testing, the ground product can be used as the light-enabled light-emitting material in the near infrared region. The adopted material is a potential material for the light-emitting layer of near-infrared LEDs. Nonetheless, the technology is still immature for application. Further researches are still required on the fabrication method of the light-emitting layer.
Accordingly, owing to the wide applications of near-infrared LEDs and difficulties in fabrication, the present invention provides a novel improvement on the composition of the light-emitting layer of a near-infrared LED and the method for manufacturing the same.